Class Message

All communications inside of the domain protocol are carried in a single format called a message.

Inheritance

Object

DnsObject

Message

Implements

IWireSerialiser

ICloneable

Inherited Members

DnsObject.CreationTime

DnsObject.Length()

DnsObject.Clone()

DnsObject.Clone<T>()

DnsObject.Read(Byte[])

DnsObject.Read(Byte[], Int32, Int32)

DnsObject.Read(Stream)

DnsObject.ToByteArray()

DnsObject.Write(Stream)

Object.Equals(Object)

Object.Equals(Object, Object)

Object.ReferenceEquals(Object, Object)

Object.GetHashCode()

Object.GetType()

Object.MemberwiseClone()

Namespace: Makaretu.Dns

Assembly: Makaretu.Dns.dll

Syntax

public class Message : DnsObject, IWireSerialiser, ICloneable

Fields

MaxLength

Maximum bytes of a message.

Declaration

public const int MaxLength = 9000

Field Value

Type	Description
Int32	9000 bytes.

Remarks

In reality the max length is dictated by the network MTU. For legacy IPv4 systems, 512 bytes should be used. For DNSSEC, at least 4096 bytes are needed.

9000 bytes (less IP and UPD header lengths) is specified by Multicast DNS.

MinLength

Minimum bytes of a messages

Declaration

public const int MinLength = 12

Field Value

Type	Description
Int32	12 bytes.

Properties

AA

Authoritative Answer - this bit is valid in responses, and specifies that the responding name server is an authority for the domain name in question section.

Note that the contents of the answer section may have multiple owner names because of aliases.The AA bit corresponds to the name which matches the query name, or the first owner name in the answer section.

Declaration

public bool AA { get; set; }

Property Value

Type	Description
Boolean	true for an authoritative answer; otherwise, false.

AD

Authentic data.

Declaration

public bool AD { get; set; }

Property Value

Type	Description
Boolean	true if the response data is authentic; otherwise, false.

Remarks

Only used in a response and indicates that all the data included in the Answers and AuthorityRecords sections are authenticated by the server according to its DNSSEC policies.

AdditionalRecords

The list of additional records.

Declaration

public List<ResourceRecord> AdditionalRecords { get; set; }

Property Value

Type	Description
List<ResourceRecord>	A list of additional resource records.

Answers

The list of answers.

Declaration

public List<ResourceRecord> Answers { get; set; }

Property Value

Type	Description
List<ResourceRecord>	A list of answers.

AuthorityRecords

The list of authority records.

Declaration

public List<ResourceRecord> AuthorityRecords { get; set; }

Property Value

Type	Description
List<ResourceRecord>	A list of authority resource records.

CD

Checking disabled.

Declaration

public bool CD { get; set; }

Property Value

Type	Description
Boolean	true if the query does not require AD; otherwise, false.

Remarks

Only used in a query and indicates that pending (non-authenticated) data is acceptable to the resolver sending the query.

DO

Indicates that DNS Security Extensions (DNSSEC) are supported.

Declaration

public bool DO { get; set; }

Property Value

Type	Description
Boolean	true if DNSSEC is supported; otherwise, false.

Remarks

The DO bit is actually in the OPTRecord, when setting the record is added to AdditionalRecords if not already present.

See Also

UseDnsSecurity()

https://tools.ietf.org/html/rfc3225

Id

A 16 bit identifier assigned by the program that generates any kind of query. This identifier is copied the corresponding reply and can be used by the requester to match up replies to outstanding queries.

Declaration

public ushort Id { get; set; }

Property Value

Type	Description
UInt16	A unique identifier.

IsQuery

Determines if the message is query.

Declaration

public bool IsQuery { get; }

Property Value

Type	Description
Boolean	true for a query; otherwise, false for a response.

IsResponse

Determines if the message is a response to a query.

Declaration

public bool IsResponse { get; }

Property Value

Type	Description
Boolean	false for a query; otherwise, true for a response.

Opcode

The requested operation.

Declaration

public MessageOperation Opcode { get; set; }

Property Value

Type	Description
MessageOperation	One of the MessageOperation values. Both standard and extended values are supported.

Remarks

This value is set by the originator of a query and copied into the response.

Extended opcodes (values requiring more than 4 bits) are split between the message header and the OPTRecord in the AdditionalRecords section. When setting an extended opcode, the OPTRecord will be created if it does not already exist.

See Also

CreateResponse()

QR

A one bit field that specifies whether this message is a query(0), or a response(1).

Declaration

public bool QR { get; set; }

Property Value

Type	Description
Boolean	false for a query; otherwise, true for a response.

Questions

The list of question.

Declaration

public List<Question> Questions { get; }

Property Value

Type	Description
List<Question>	A list of questions.

RA

Recursion Available - this be is set or cleared in a response, and denotes whether recursive query support is available in the name server.

Declaration

public bool RA { get; set; }

Property Value

Type	Description
Boolean	true if recursion is available; otherwise, false.

RD

Recursion Desired - this bit may be set in a query and is copied into the response. If RD is set, it directs the name server to pursue the query recursively.

Recursive query support is optional.

Declaration

public bool RD { get; set; }

Property Value

Type	Description
Boolean	true if recursion is desired; otherwise, false.

Status

Response code - this 4 bit field is set as part of responses.

Declaration

public MessageStatus Status { get; set; }

Property Value

Type	Description
MessageStatus	One of the MessageStatus values.

TC

TrunCation - specifies that this message was truncated due to length greater than that permitted on the transmission channel.

Declaration

public bool TC { get; set; }

Property Value

Type	Description
Boolean	true for a truncated message; otherwise, false.

See Also

Truncate(Int32)

Z

Reserved for future use.

Declaration

public int Z { get; set; }

Property Value

Type	Description
Int32	Must be zero in all queries and responses.

Methods

CreateResponse()

Create a response for the query message.

Declaration

public Message CreateResponse()

Returns

Type	Description
Message	A new response for the query message.

Read(WireReader)

Reads the DNS object that is encoded in the wire format.

Declaration

public override IWireSerialiser Read(WireReader reader)

Parameters

Type	Name	Description
WireReader	reader	The source of the DNS object.

Returns

Type	Description
IWireSerialiser	The final DNS object.

Overrides

DnsObject.Read(WireReader)

Remarks

Reading a ResourceRecord will return a new instance that is type specific unless the GetDataLength() is zero.

ToString()

Declaration

public override string ToString()

Returns

Type	Description
String

Overrides

Object.ToString()

Truncate(Int32)

Make the message not exceed the specified length.

Declaration

public void Truncate(int length)

Parameters

Type	Name	Description
Int32	length	The maximum number bytes for the message.

Remarks

If the message does not fit into length bytes, then AdditionalRecords are removed and then AuthorityRecords are removed.

If it is still too big, then the TC bit is set.

UseDnsSecurity()

Enables DNS Security Extensions (DNSSEC) for the message.

Declaration

public Message UseDnsSecurity()

Returns

Type	Description
Message	The Message for a fluent design.

Remarks

Sets DO to true. Adds an OPTRecord to AdditionalRecords if not already present.

See Also

DO

Write(WireWriter)

Writes the DNS object encoded in the wire format.

Declaration

public override void Write(WireWriter writer)

Parameters

Type	Name	Description
WireWriter	writer	The destination of the DNS object.

Overrides

DnsObject.Write(WireWriter)

Implements

IWireSerialiser

System.ICloneable